1. Field of the Invention
The present invention relates to an optical waveguide with a light-emitting element having a novel branched structure for generating a plurality of light beams from one light-emitting element. And the present invention also relates to an optical touch panel having the optical waveguide with a light-emitting element.
2. Description of the Related Art
Conventionally, an optical waveguide with a light-emitting element having a branched structure for generating a plurality of light beams from one light-emitting element is known (For example, US 2006/0188198 A1). This kind of optical waveguide with a light-emitting element is preferably used for emitting light beams to a coordinate input region of an optical touch panel.
FIG. 8 shows an optical waveguide 40 with a light-emitting element having a conventional branched structure. In the conventional optical waveguide 40 with a light-emitting element, a plurality of branch points 42 are provided in a direction orthogonal to a light guiding direction 45 of a main path 44 in a core 43 to distribute light emitted from a light-emitting element 41 to respective branched paths 46.
The optical waveguide 40 with such a structure suffered from a wide width W2 of the main path 44 (a cladding layer is filled in each gap 47) because gaps 47 were needed to be located among adjacent branched paths 46. Further, there were such problems that the optical waveguide 40 with a light-emitting element tended to have differences in optical transmission efficiency among the branched paths 46 due to big difference in length among respective branched paths 46 and the intensity of light emitted from respective branched paths 46 tended to be nonuniform.
The optical waveguide 40 with a light-emitting element having a conventional branched structure had a disadvantage of having a wide width W2 of the main path 44 because the plurality of branched points 42 were provided in a direction orthogonal to the light guiding direction 45 in the main path 44. Moreover, the optical waveguide 40 with a light-emitting element also had such a disadvantage that the intensity of light emitted from respective branched paths 46 tended to be nonuniform due to big difference in length among respective branched paths 46.
It is an object of the present invention to realize an optical waveguide with a light-emitting element having a structure in which the width of the main path is narrower than the conventional one and the intensity of light beams emitted from each branched path is uniform.